Make the au jus

• Sauté the onion and garlic in a little butter until soft.
• Pour in the beef stock, Worcestershire sauce and soy sauce, season with black pepper and simmer.

Warm the beef

• Add the roast beef to the simmering broth for a few minutes to warm through, then lift it out.

Build the sandwiches

• Spread butter on the split baguettes.
• Layer the beef and provolone inside.

Toast and serve

• Bake the sandwiches until the cheese melts and the bread is crisp.
• Serve hot with the au jus on the side for dipping.